Process for the production of hydroperoxides of partially hydrogenated polycyclic aromatic hydrocarbons



States Rudolf Heise, Dusseldorf-Holthausen, Germany, assignor toDehydag, Deutsclie Hydrierwerke G. m. b. H., Dusseldorf, Germany, acorporation of Germany No Drawing. Application February 1, 1955 SerialNo. 485,598

Claims priority, application Germany February 4, 1954 3 Claims. (Cl.204-162) This invention relates to a process for the production ofhydroperoxides of partially hydrogenated polycyclic aromatichydrocarbons, and more particularly to the oxidation of such aromatichydrocarbons into the correspondmg hydroperoxides with the aid of anoxidizing gas, in the pi-(esence of fluorescent dyes, such aschlorophyll and the It has long been known that tetrahydronaphthalenetends to undergo an auto-oxidation reaction when it is brought intocontact with oxygen or oxygen-containing gases. In this reaction thetetrahydronaphthalene takes up one mol of oxygen to form an oxidationproduct the structure of which has been ascertained to be 1,2,33,4-tetrahydronaphthalene-l-peroxide .(a-tetrahydronaphthalene peroxide).The product, which is essentially colorless, is however simultaneouslydiscolored by this autooxidation and turns more or less yellow.

It is also known that such an auto-oxidation reaction can be materiallyaccelerated by passing the oxygen or oxygen-containing gas through thetetrahydronaphthalene in a finely divided form and maintaining thetemperature of the reaction mixture above room temperature in order toincrease the rate of oxidation.

As a further improvement of this auto-oxidation reaction, the prior artalso discloses the use of suitable catalysts. For example, it is knownthat tetrahydronaphthalene peroxide itself is an effective catalyst. Inaddition, prior workers in this field have found that certain metals andtheir compounds are effective catalysts; thus, it is known that theauto-oxidation of tetrahydronaphthalene intoits peroxide can beaccelerated by the presence of copper, tin, lead, and the oxides andcarbonates of these metallic elements, or by the presence of cobalt inthe form of its naphthenates. Within recent years it was also found thatmanganese stearate is a very effective catalyst.

While the above catalyst tends to accelerate the oxidation of partiallyhydrogenated polycyclic aromatic hydrocarbons into their hydroperoxidesand produce improved yields, the methods employed by the prior art donot pro duce commercially attractive yields, and the oxidation productsobtained by these methods are often discolored by undesirabledissociation products and polymerizates.

It is one object of the present invention to provide a method ofoxidizing partially hydrogenated polycyclic aromatic hydrocarbons intotheir hydroperoxides which will produce commercially attractive yieldsof such hydroperoxides.

Another object of the present invention is to provide a method ofoxidizing partially hydrogenated polycyclic aromatic hydrocarbons intotheir hydroperoxides which will yield the desired product in asubstantially pure form uncontaminated by undesirable dissociation andpolymerization products.

Still another object of the present invention is to provide catalystsfor the oxidation of partially hydrogenated iolycyclic aromatichydrocarbons into the corresponding atom hydroperoxides which willproduce higher yields of uncontaminated pure hydroperoxides.

Other objects and advantages of this invention will become apparent asthe description thereof proceeds.

I have found that the transformation of partially hydrogenatedpolycyclic aromatic hydrocarbons into their corresponding hydroperoxidescan be carried out much more rapidly and with much improved yields overthe methods of the prior art, by oxidizing such hydrocarbons with oxygenor oxygen-containing gases in the presence of sensitizable organic dyes,i. e. organic dyes which absorb certain portions of the spectrum, andwhile exposing the reaction mixture, including said organic dye, tolight. The reaction according to my invention is preferably carried outat elevated temperatures and at atmospheric or elevated pressure.

Examples of partially hydrogenated polycyclic aromatic hydrocarbonsWhich may be oxidized into the corresponding hydroperoxides by themethod according to my invention are tetrahydropnaphthalene,octahydronaphthalene, benzene-alkyl-tetrahydronaphthalene,tetrahydroanthracene, octahydroanthracene, tetrahydropenanthrene,octahydrophenanthrene, tetrahydroacenaphthene, and the like.

The sensitizable organic dye is dissolved in the reaction mixture anduniformly distributed therethrough in a fluorescent state, whereby thequanta of light absorbed by the dye are released to every particle ofthe reaction mixture uniformly throughout the solution, producing acatalyzing photochemical eifect.

Examples of suitable sensitizable organic dyes are chlorophyll, metalcomplex compounds such as the phthalocyanins, fluorescein,dinaphthylenedioxide, phenylbenzimidazole, phenyldlmethylacridine, andthe like. Of these, however, chlorophyll has been found to be the mostdesirable catalyst because of its superior photochemical eflect.

The above-named fluorescent dyes, and particularly chlorophyll, absorbprimarily those quanta of light which have a relatively long wavelength, i. e. those Which lie in the red and yellow range of thespectrum. Hence, the most suitable sources of light which may be usedfor irradiating the reaction mixture in accordance with my invention aresunlight and incandescent light sources, both of which contain a largeamount of red and yellow light quanta. Electric incandescent lightsources have the advantage that they simultaneously furnish some of theheat required for the oxidation reaction.

The transformation of partially hydrogenated polycyclic aromatichydrocarbons into their corresponding hydroperoxides can also beaccelerated by carrying out the oxidation in accordance with myinvention at temperatures between 20 C. and 120 C., particularly between60 C. and C. The prevailing pressure may be either atmospheric pressureor an elevated pressure.

The process of oxidizing partially hydrogenated polycyclic aromatichydrocarbons into their hydroperoxides according to my invention has twodistinct advantages over the processes heretofore known. First, theoxidation takes place within a much shorter time and produces muchbetter yields than the known processes, and secondly, the short timerequired to reach a certain peroxide content practically eliminatesundesirable side reactions, which tend to decoinpose the hydroperoxideformed and produce dark, tar-like dissociation products if the oxidationreaction requires an extended period of time.

The following example will further illustrate my invention and enableothers skilled in the art to understand my invention more completely. Itis understood, however, that the present invention is not limited to theexample.

Example Three identical glass tubes, each having an internal volume of650 c c., were closed ofi at one end with sin- 'tered glass or ceramicfritl The other end of each tube was provided with a sphericalenlargement to -receive the foam' formed during the oxidation reaction.I Each tube was also'providedwith a water jacket'to maintain thetemperature substantially constant during the reaction.

The three tubes were then filled withtechnical gradetetrahydronaphthalene having a density of 0.968 at C. until the levelof'liquid in the threetubes reached 50 cm. above the bottom. -A'finelydivided, uniform stream of air, dried over concentrated sulfuric acid,was-then passedtlir'ou'gh' the"tetrahydronaphthalene in each tube" V L'and'the temperature was adjusted to between 7 C. and

The 'oxidationof tetrahydronaphthalene in tube No. 1

was permittedto proceed in the absence of any catalyst whatsoever. Tothe reaction mixture in tube No.,2,'0.1% by weight of manganeSeJstearatebased on theweight of tetrahydronaphthalene was added. The reactionmixture in tube No. 3 was modified by the addition 050.1% by 'weight.ofroil-soluble, copper-free chlorophyll and the tube'was exposed tolight which was rich in red and yellow light quanta. 1 J

The progress of theioxidation in each of,the three tubes was followed bydetermining the peroxide content by iodometrictitration and periodicmeasurement of the density of thereaction mixture. I

The period of observation extended over 24 hours since it is known thatduring that period the density and the peroxide content increaseuniformly and steadily,

whereas if the reaction is allowed to continue over a longer period oftime the density of the reaction mixture .continues to increase whilethe peroxide content, after having reached a certain maximum value,begins to decrease due to decomposition reactions Since the oxidationreactions in the three tubes were carried out under identical conditionsexcept with respect to the presence of a catalyst and the exposure tolight in the case of tube No. 3, an excellent basis for comparison wasgiven. Such a comparison confirmed the known fact that the oxidation oftetrahydronaphthalene into its peroxides in the presence of manganesestearate as a .catalyst proceeds much more rapidly than the oxidation inthe absence of a catalyst. In addition, the comparison of the periodicmeasurements of density and peroxide content surprisingly showed thatthe photochemical oxida- .tion in the presence of chlorophyll whileexposing the reaction mixture to light proceeds much more rapidly thanthe oxidation in the presence of manganese stearate.

. In other words, the oxidation in tube No.' 3 produced considerablyhigher yields of tetrahydronaphthalene .peroxide in the same period oftime.

More particularly, the following data were obtained: The density of thereaction mixture in tube No. 1 at the end of 24 hours had increased from0.968 at 20 C.

to 0.987 at 20 C. In tube No. 2 the density at the end of 24 hours hadincreased to 0.996 at 20 C.', and in tube-No. 3 the photochemicaloxidation had increased the density of the reaction mixture to 1.005 at20 C. Similarly, the content of tetrahydronaphthalene peroxide in tubeNol 1 at the end of 24 hours was 17% and in tube No. 2 it was 27%; intube No. 3 itwas 37%.

Comparison of the periodic measurements of density and peroxide contentin the three tubes respectively showed that the yields produced by theoxidation reaction catalyzed by manganese stearate after 24 hours, are

produced by'the photochemical reaction in accordance with the presentinvention after only 15 to 16 hours, i. e.

tacting' it in that form with the oxidizing gas.

While. I have. disclosed certain specific embodiments of myinventiomfIwish it to. be understood that various changes and modifications can bemade therein without.

peroxide, which comprises passing air through tetrahydronaphthalene at atemperature from 70-75" C. in I the presence ofchlorophyll whileexposing the reaction within of the amount of time. Similarly, theyields produced by the uncatalyzed oxidation reaction after 24 hours,are produced by the photochemical oxidation reaction after only 11-12hours, i. e. in half the time.

The reaction product obtained by the process in accordance with 'thepresent invention is a solution of tetrahydronaphthalene peroxide intetrahydronaphthalene. The solution is practically free from dark,tar-like, decomposition or polymerization products; The raw product mayreadily be purified by methods well known in the art to yieldtetrahydronaphthalene peroxide of high purity. Both the raw and thepurified'product are well suited as intermediate products in the'production of hydroaromatic alcohols, ketones and carbbxylic'acids; as

initiators for polymerization processes, as oxidizing and bleachingagents, and for many other industrial purposes. The intimate admixtureof the tetrahydronaphthalene with the oxidizing gas is relativelyimportant, for the etficient performance ofthe process according to myinvention. This intimate admixture can be brought about in a variety ofways. In addition to introducing the oxygen or oxygen-containing gas ina finely divided state into the partially hydrogenated polycyclicaromatic hydrocarbon, the hydrocarbon may also be brought in intimatecontact withv the gas in counter-current fashion, for example bytrickling the hydrocarbon downwardly over Raschig rings or the likeagainst aistream of rising,pre-

heated oxidizing gases. Still another method is to atomize thehydrocarbon into a mist or fog and then condeparting from the spirit ofmy invention or the .scope of the appended claims.

According to the procedure of the above-mentidned example, otherpartially hydrogenated polycyclic aromatic hydrocarbons may be oxidized,such as octahydr'onaphthalene, benzene-alkyl-tetrahydronaphthalenes,ara'lkyltetrahydronaphthalenes, tetrahydroanthracene and:trahydrophenanthrene. I] claimz 1. The method of tially hydrogenatednaphthalene derivatives, whichpomprises passing an oxygen-containing gasthrough apartially hydrogenated naphthalene at a temperature between 20and C. in ,the presence of a light-sensitizable organic dye' selectedfrom the group consisting of chlorophyll, phthalocyanins, fluorescein,dinaphthylenedioxide,'phenylbenzimidazole and phenyldimethylacridine,

while exposing the reaction mixture to light.

2.The method of producing 'tetrahydronapthal'ene mixture to light.

3. The method of producing tetrahydronaphthalene peroxide as'in claim 2,wherein the light to which the reaction mixture is exposed is rich inred and yellow light quanta. r I

References Cited in the file of this patent UNITED STATES PATENTS2,165,130 2,435,763 Vaughan et al. Feb; 10,1948 2,543,817 Weil Mar.6,19511 2,727,857 Carter Dec. 20, 1955 producing hydroperoxides ofipafr-A July 4. 1939'

1. THE METHOD OF PRODUCING HYDROPEROXIDES OF PARTIALLY HYDROGENATEDNAPHTHALENE DERIVATIVES, WHICH COMPRISES PASSING AN OXYGEN-CONTAININGGAS THROUGH A PARTIALLY HYDROGENATED NAPHTHALENE AT A TEMPERATUREBETWEEN 20 AND 120*C. IN THE PRESENCE OF A LIGHT-SENSITIZABLE ORGANICDYE SELECTED FROM THE GROUP CONSISTING OF CHLOROPHYLL, PHTHALOCYANINS,FLUORESCEIN, DINAPHTHYLENEDIOXIDE, PHENYLBENZIMIDAZOLE ANDPHENYLDIMETHYLACRIDINE, WHILE EXPOSING THE REACTION MIXTURE TO LIGHT.